Transparent flowable pyroxylin composition.



UNITED STATES PATENT OFFICE.

JOHN H. STEVENS, OF NElVARK, NEW JERSEY, ASSIGNOR TO THE OELLULOIDCOMPANY, OF NElV YORK, N. Y., A CORPORATION OF NEW JERSEY.

TRANSPARENT FLOWABLE PYROXYLIN COMPOSITION.

SPECIFICATION forming part of Letters Patent No. 630,945, dated August15, 1899.

Application filed January 19, 1899. Serial No. 702,636. (No specimens.)

To all whom it may concern:

Beitknown that I, J OHN H. STEVENS, of the city of Newark, county ofEssex, and State of New Jersey, have invented certain new and usefulImprovements in Transparent Flowable Pyroxylin Compositions of Matter,of which improvements the following is a specification.

Pyroxylin or nitrocellulose is formed by subjecting cotton, paper, orother cellulose fiber to the action of nitric and sulfuric acids. It isa substance which presents many varieties 0r kinds, dependent on thereaction between the cellulose and nitrous elements of I 5 theacid-bath.

The classification of pyroxylin has been based on the amount of nitrogenor nitro elements present,butalso and chiefly on its solubility indifferent menstrua known as sol- 2o vents of pyroxylin.

In making flowable pyroxylin solutions for use in the arts as varnishes,lacquers, and for waterproofing purposes the classification based onsolubility is generally the only one kept in view. Hence thecompositions to which my invention pertains demand a pyroxylin which issoluble in the ordinary liquid menstruasuch as wood-spirit, acetone,methyl acetate, amyl acetate, alcohol ether,

&c.all of which are wellknown and used for these purposes.

The strictly chemical classification of pyroXylin is useful forexplosives, and the varying solubility of pyroxylins having the samechemical composition is of less importance in making explosives than theamount of nitrogen present, because it is the amount of nitrogen gasliberated on explosion which determines the usefulness of the pyroxylino employed for such purpose.

Pyroxylin compounds can be divided into manyclasses. One of theimportant classes, however, is that of collodions or flowable solutions,which are made by simplydissolving ordinary soluble pyroxylin insufficient solvent to form the proper consistency.

lVhile many pyroxylin compounds are ofa non-transparent nature, thereare certain purposes for whlch high transparency is desired, especiallyin the final film deposited after the solvents have been evaporated.

Pyroxylin and its compounds are more or less liable to a decompositionwhich results in the generation of free acid. This is hindered by thepresence of solvents or the dissolved condition; but unless apreservative substance is present there is always danger of theevolution of acid, which is detrimental, and especially to the finalfilm deposited on drying, because a film of an acid nature will attackmetals, lose its luster, and be otherwise damaged. \Vhile thisdecomposition is more liable to affect solid pyroxylin compounds, andespecially those which are subjected to heat, nevertheless it is adetriment to the liquid compounds, although this has not been generallyrecognized.

I have traced many of the imperfect-ions in liquid compounds to thedecomposed condition and corrosive action of the unprotected r70pyroxylin. I have observed even highly-fluid solutions turned so acidthat they would strongly corrode metals dipped into them, and I havefound that much of the discoloration often observed in films made fromevaporated solutions is due to the partly-decomposed pyroxylin.

lVhile there are plenty of known means of securing stability innon-transparent pyroxylin solutions and plenty of substances which willdissolve in pyroxylin solvents and form a transparent mixture so long asthe solvent is present, there are very few substances known which willdry transparent in the final film and at the same time act as preservingagents, so as to keep the film in a permanent neutral condition withoutcausing discoloration, lack of surface brilliancy, or other defects.Hence any composition of matter which has the desired properties dependson study and experiment, especially with proportions, the properties ofsubstances, and their behavior during the evaporation of the solventsand final solidifying of the residues.

While, as before stated, little attention has been given to thestability of these flowable preparations, the diificulty in obtainingsuitable antacid or preserving agents for exploture.

sives and also solid manufacturing pyroxylin compounds has shown thatsuccessful antacid agents must necessarily be selected from a largenumber of substances which might be expected to yield good results, butwhich fail in the trial.

Experience has shown that some substances, while known as neutralizersof acid, injure nitrocellulose compounds by aiding or invitin gdecomposition, and some cause discoloration, and most of them areincompatible with transparency.

The. present invention is based on the peculiar properties residing incertain solid bodies which are non-solvents of the pyroxylin commonlyemployed in making fiowable solutions, and its distinctive noveltydepends on my discovery that the important properties of transparencyand chemical permanency, especially in the dried film or final product,are indispensably associated with the proportions of these bodies used.As a further proof of the novel use I make of these new bodies I canstate that while one of them has been suggested to be used in connectionin a lim-. ited way with a certain kind of pyroxylin, known astetranitrocellulose and in larger proportions than would be useful in mycompounds it has been so suggested as an equivalent for a number ofother bodies which are totally unfit for my purposes in any proportion,for these bodies would fail to give chemical stability and many of themwould be detrimental in other respects. Forinstance, they would act onthe film in such a Way as to destroy its luster.

.The group of bodies to which I refer and which are included within myinvention are known as the zinc salts of the volatile monatomic fattyacids. The principal acids of this group are formic, acetic, propionic,butyric, and valeric acids, and I confine my invention to the zinc saltsof these acids. The salts resulting from the chemical combination ofthese acids with zinc are zinc form ate, zinc acetate, zinc propionate,zinc butyrate, and zinc valerate. These are the salts which form onepart of my new flowable transparent composition of matter. I have usedthese salts successfully and have determined by experiment theirrelative value for the purpose. While they all possess more or lessantacid power, I prefer to use the salts which are most easily soluble,especially in woodspirit. By soluble of course I mean (as is usuallymeant by the term) in the cold. I have found that acetate of zinc givesevery efiect required and has the advantage of cheapness. A goodproportion when using any of these zinc salts is one per cent. to theweight of the pyroxylin present in the mix- More (up to five per cent.)or less can be used; but the operator must bear in mind that a lessamount will give decreased stability, although I find that in thesecompounds one-half of one per cent. gives very fair results. As tolarger proportions, they will tend to cloud or weaken the compounds,especiall y in the residues after evaporation, unless they are employedin moderation. \Vhen five per cent. is exceeded, the solutions makeclouded ordiscolored effects or result in other undesirable properties.

The manufacture of flowable' pyroxylin solutions is well understood byoperators in this art. The particular solvent employed and the fluidityor stiffness of the solutions are questions of judgment, based on whatis well known of the properties of the ingredicuts and application ofthe mixtures. Some of the most important compounds are in the form of apaste.

By fiowable solutions I mean such solutions as can be flowed or spread,as distinguished from solutions which are too stilf to be worked in thecold. The non-flowable so lutions are solid pyroxylin compounds,whichgenerally are manipulated in rolls or equivalent mixing machinery andformed into shape afterward by being pressed into masses or blocks,which, if desired, can be cutinto sheeting. These compounds are alsoforced through nozzles into such forms as tubes, rods, and strips.

While I am unable to explain why a basic substance already saturatedwith an acid can act as a preserving agent and prevent the deleteriousaction of the corrosive nitro compounds in decomposing pyroxylin, myexperiments have nevertheless demonstrated this to be a fact. I can onlystate thatit seems to depend on the nature of the acid radical presentin the preserving agent. Even when the elements contained in thesepreserving salts are united to other substancesfor instance, in neutralsalts containing dissimilar acid radicalsthe resultant compound saltpossesses preserving power at least in proportion approximating to theamount of such element present. Chloracetate of zinc is an example ofsuch compound salt. As an instance of the eifect of the nature of theacid radical present in these preserving salts I can state that I havefound by experiment that while zinc acetate is a good antacid substancein connection with pyroxylin, sulfite of zinc and chlorid of zinc aretotally unsuitable as ingredients in my compounds. Perfect solubility ofthe salt in the solvent em-. ployed and the ability to formhighly-transparent effects do not give the salt antacid power, for Ihave found that chlorid of zinc dissolves in wood-spirit andgrain-alcohol and forms a highly-transparent combination with thepyroxylin compounds, while at the same time it is useless for antacidpurposes in my compounds. Besides lacking the necessary preserving powerI find that compounds made with deliquescent chlorids attract moisture,and hence articles coated with a pyroxylin compound containing thechlorids of zinc or calcium become wet on the surface, which attractsdust and detracts from the necessary luster. While the chlorid salt canbe washed away from the surface, it is always liable to exude from thebody of the material and form fresh deposits.

I am aware that one of the members of my new group of antacidsubstancesnamely, acetate of zinchas been proposed as a solvent of acertain kind of pyroxylin known as tetranitrocellulose in connectionwith alcohol and methylated spirit and as a substitute and equivalentfor calcium chlorid and zinc chlorid, the proportion to be used beingabout five per cent. to the amount of alcohol employed. It necessarilyrequires such excessive proportions of solvent for fiowable solutionsthat the suggested proportions of zinc acetate are very much larger thanthe proportions I have found to be useful. \Vhile a solution oftetranitrocellulose in alcohol containing about five per cent. of thezinc acetate to the alcohol would doubtless present a transparentappearance, an y attempt to evaporate the solution would result in anontransparent film, besides which it is by no means certain that zincacetate has been suggested for use in fiowable solutions of even theparticular kind of pyroxylin known as tetranitrocellulose, because suchsuggestion has always been coupled with instructions to select such fromamong the numerous solvents mentioned as would be best fitted for thespecial purpose in view. As the other substances mentioned includestrong solvent esters, it is not certain that zinc acetate has beensuggested to be used in fiowable solutions. The fact that none of thevarious kinds of pyroxylin commonly used in making fiowable solutionsare soluble in an alcoholic solution of zinc acetate has some bearing onthis point.

Acetate of zinc will not aid alcohol (either ethylic or methylic) indissolving the ordinary kind of pyroxylin used for fiowablecompositions; but my experiments have positively demonstrated that itretards or weakens the solvent power directly as to the amount presentin the alcohols. For instance, a five-percent. solution inninety-five-per-cent. ethylic alcohol will not dissolve the ordinarypyroxylin when the alcohol is even in large excess and at the end of twodays contact at ordinary atmospheric temperatures. By using a niethylicalcohol so weak with water that it barely dissolves pyroxylin I findthat a saturated solution of zinc acetate in this weak alcohol is anabsolute non-solvent. Besides this my experiments have demonstrated thatall proportions in which zinc acetate has been. recommended to be usedwould fail to give a final transparency. I believe, therefore, that I amthe first to discover and apply the proper proportions of zinc acetatefor manufacturing a fiowable transparent pyroxylin compound which willremain transparent when evaporated to a dry residue or film.

While I include in my invention the zinc salts of the volatile monatomicfatty acids as preserving agents for fiowable transparent pyroxylinsolutions, whether the salts are simple,compound,mixed,or combinedchemically with other salts or compounds, I exclude any combination ofthe salts of this specification with the halogen acids, for suchcompounds have already been secured to me in United States Patent No.614,514, of November 22, 1898, which patent includes such substances,for instance, as chloracetate of zinc, chlorpropionate of zinc,ehlorbutyrate of zinc, &c.

In the United States Letters Patent granted to me April 4, 1899, No.622,29et, I have described and claimed the use of the zinc salts 'of thevolatile monatomic fatty acids herein referred to when used in pyroxylincompounds containing camphor as an ingredient; but my present inventionis based on the discovery that the zinc salts of the volatile monatomicfatty acids herein referred to and described are useful as apreservative of pyroxylin compounds which do not contain camphor whenused as herein described and set forth.

Having thus'fully described my invention, what I claim, and desire tosecure by Letters Patent, is-- 1. A fiowable, transparent composition ofmatter consisting of pyroxylin, a solvent of the same, and a zinc saltof the group consisting of formate of zinc, acetate of zinc, propionateof zinc, butyrate of zinc, and valerate of zinc, the said salt beingpresent in pro portion not exceeding five per cent. of the amount ofpyroxylin, substantially as described.

2. A fiowable transparent composition of matter containing pyroxylin, asolvent of the same, and acetate of zinc, in proportions not exceedingfive per cent. of the pyroxylin, substantially as described.

JOHN H. STEVENS.

Vvitnesses:

WALTER P. LrNnsLEY, 1W1. R. EISELE.

